For convenience purposes, it is well known to provide garage doors which utilize a motor to provide opening and closing movements of the door. Motors may also be coupled with other types of movable barriers such as gates, windows, retractable overhangs and the like. An operator is employed to control the motor and related functions with respect to the door. The operator receives command signals for the purpose of opening and closing the door from a wireless remote, from a wired or wireless wall station or other similar device. It is also known to provide safety devices that are connected to the operator for the purpose of detecting an obstruction so that the operator may then take corrective action with the motor to avoid entrapment of the obstruction.
How safety devices are used with a door operator system have evolved from the days of no uniform standard to the currently applied government regulations as embodied in Underwriters Laboratories Standard 325. UL Standard 325 encompasses safety standards for a variety of movable barriers such as gates, draperies, louvers, windows and doors. The standard specifically covers vehicular gate or door operators intended for use with garages and/or parking areas. Such devices require a primary safety system and a secondary safety system which are independent of each other. Primary entrapment systems sense the operator motor's current draw, or motor speed and take the appropriate corrective action if the monitored value is exceeded. Primary systems must be internal within the operator head. Secondary entrapment systems are typically external from the operator head and may include a non-contact or contact type sensor. But, secondary systems may also be internal to the operator head as long as they are independent of the primary system.
One of the more widely used non-contact devices is a photo-electric eye which projects a light beam across the door's travel path. If the light beam is interrupted during closure of the door, the operator stops and reverses the travel of the door. Contact type safety devices such as an edge-sensitive pressure switch, which is attached to the bottom edge of the door and runs the complete width of the door, may also be used. Other contact safety devices directly monitor the operating characteristics of the driving motor to determine whether an obstruction is present. Typically, shaft speed of the motor is monitored by projecting an infrared light through an interrupter wheel. Alternatively, Hall effect switches or tachometers can be used to monitor shaft speed. Or, the motor current could be monitored such that when an excessive amount of current is drawn by the motor—which indicates that the motor is working harder than normal—it is presumed that an obstruction has been encountered. It is also known to monitor door speed with a sliding potentiometer, wherein a rate of change is equated to the speed of the door and wherein unexpected slowing of the door triggers corrective action by the operator. The secondary entrapment requirement may also be met by providing an operator that is capable of receiving continuous pressure on an actuating device that is in the line of sight of the door and maintains the opening or closing motion until the respective limit position is reached. Regardless of how the safety devices work, their purpose is to ensure that individuals, especially children, are not entrapped by a closing door. Opening forces of the door are also monitored to preclude damage to the operating system for instances where an object or individual is caught upon a door panel as the door moves upwardly.
One particular feature of the standard requires that when an operator controls a pinch-resistant door and an external secondary entrapment device is not connected to the operator, then a fifteen pound obstruction force threshold setting must be used. In other words, if no external secondary entrapment device is attached to the operator but instead an internal secondary entrapment device is used, then the maximum force that the motor is allowed to apply to the door—in a closing direction—is fifteen pounds. But, if an external secondary entrapment device is attached, then the UL standard does not require a maximum obstruction force setting.
In some operator systems, if the end-user selects an operator model without the external secondary entrapment feature, then an input jumper switch is set to disable and the fifteen pound force threshold is used during barrier movement. If the end-user selects an operator model with the external secondary entrapment feature, then the input jumper is permanently enabled and the force threshold value is set at a higher value, typically twenty-five pounds. If the end-user desires to later add the external secondary entrapment feature, then the jumper must be physically moved from a disabled position to an enabled position. If the jumper is not moved to an enabled position then the external secondary entrapment feature will work, but the force threshold remains at fifteen pounds.
It has been found that the fifteen pound threshold is quite sensitive and as a result phantom obstructions are encountered. In other words, the operator falsely detects and reacts to a non-existent obstruction in the barrier's path. Such false detections may be the result of the wind, temperature, debris in the door track and the like. These false detections cause the barrier to reverse direction and require the user to wait unnecessarily for the barrier to complete its opening or closing cycle.
Other garage door operators incorporating a secondary inherent safety system allow the installer to add the secondary external safety system. Usually there is a “factory installed jumper” on a main motor control board of the operator that selects the external safety system. When the jumper is intact, the secondary external safety system is enabled and operational. Therefore, the secondary external safety system must be connected. Cutting the jumper and doing a pre-defined boot-up sequence removes the requirement for an external secondary safety system. Once this is done, however; the installer cannot replace or ‘uncut’ the jumper. The UL standard allows the external safety system to be installed on all door system types while the inherent safety system can only be used on specific door types (e.g. doors with pinch-resistant panels). And, since the external safety system is ‘external’ to the operator power head, it is exposed to easier damage (misaligned photo-electric sensors, damaged or cut wires, etc.). Thus, the external safety system and the operator power head act as a fail-safe system. If the external safety system is non-operational, the power head modifies its operation to try and prevent hazards (e.g. requires constant contact on a wall-control up/down button to close the door). Since the UL standard may require the external safety system for a specific door type, the simple act of disconnecting the external system safety systems does not allow an operator to automatically select the inherent safety system.
Another type of garage door operator allows two different types of external safety systems. One is a wired photo-electric sensor system and the other is the wireless photo-electric sensor system. The operator must determine which external safety system to use and have the ability to change from one type of safety system to the other. If a wired photo-electric sensor system is detected (connected and operational), then the operator remains in the wired safety system required setting. If no wired safety system is detected and then a wireless safety system is taught to the power head, then the operator changes to the wireless safety system required setting. If a wired safety system is now connected to the operator, the operator automatically changes to the wired safety system's required setting. Thus the operator has the ability to change from one type of external safety system to another type. But as in the previously discussed operator system, there is no provision for changing back to an internal secondary entrapment system. Accordingly, there is a need in the art for a method of enabling an operator to be re-programmed between different types of secondary safety systems.